The present invention generally relates to a data processing system and its storage area allocation method, and in particular can be suitably applied to a data processing system and its storage area allocation method that allocates a storage area of an externally connected storage apparatus.
In recent years, the amount of data used by corporations and individuals has increased drastically. Thus, storage systems using technology such as SAN (Storage Area Network) and NAS (Network Attached Storage) that enable flexible data management by connecting storage apparatuses and host computers via a switch or a hub are being used extensively.
When allocating a storage area (hereinafter referred to as “volume”) of a storage apparatus to be used by a host computer from the storage apparatus to the host computer under a SAN environment, there is standard technology for putting together a plurality of volumes into a group (this group is hereinafter referred to as a “storage pool” and a volume registered in the storage pool is referred to as a “pool volume”), and allocating a volume having the capacity requested by the host computer from the storage pool. Further, in order to make the volume allocation to the host computer more efficiently and easily, technology is disclosed for creating a storage pool by classifying the storage areas based on the demand characteristics, required performance and reliability of each application from the attributes of the physical disk itself, and presenting the candidate of the storage pool to be used to the user (refer to Japanese Patent Laid-Open Publication No. 2004-334561).
Meanwhile, as technology for reducing the management cost of storage apparatuses, technology referred to as thin provisioning is disclosed for allocating a virtual volume (hereinafter referred to as a “virtual volume”) to a host computer, and allocating the actual storage area according to the I/O from the host computer to the virtual volume (refer to Japanese Patent Laid-Open Publication No. 2003-15915).
When using this technology, the administrator of the storage apparatus registers in advance one or more storage areas in a logical group referred to as a thin provisioning pool (this is hereinafter referred to as a “TP pool” and a volume registered in the TP pool is also referred to as a “pool volume”). Here, the administrator sets a threshold value for warning the capacity depletion of the TP pool. The administrator thereafter creates a virtual volume, and associates it with the TP pool and the host computer.
When data is written from the host computer into the virtual volume, the written data is actually stored in the storage area of the pool volume. When the capacity that is actually being used by the TP pool approaches the threshold value as a result of data being written into the virtual volume, the management server warns the administrator. Based on this warning, the administrator takes measures such as adding a physical disk to the storage apparatus.
In a case where volumes having different attributes such as the disk type or RAID level coexist in the TP pool, in order to guarantee the reliability of the virtual volume used by the host computer, disclosed is technology that continues to store data in a volume having the same property as the pool volume to which the data was first written (refer to Japanese Patent Laid-Open Publication No. 2007-66259).
In addition, there is technology for treating a plurality of storage apparatuses as though they are a single storage apparatus for the purpose of unifying the connection relation between a host computer and a storage apparatus, or using a high capacity storage resource (such as a cache memory) in an inexpensive storage apparatus. This is disclosed as technology (hereinafter referred to as the “external storage function”) which enables the use of a volume of a separate storage apparatus as the external storage area of the self-storage apparatus (refer to Japanese Patent Laid-Open Publication No. 2005-011277). When using this technology, the storage apparatus loaded with the external storage function and the storage apparatus to be used as the external storage area are connected via a network.